This invention relates in general to surveying instruments and procedures, and in particular relates to surveying systems which employ the use of laser beams for purposes such as measuring elevation and grades.
It is common practice in civil engineering and in the construction industry to measure elevations and grades by means of a level or transit used in combination with a leveling rod, such as a Philadelphia rod, linker rod or geodetic rod. In the use of such instruments, two operators are required, one for manipulating the level and the other for holding the rod. Measurements taken by the use of such instruments are subject to a number of inaccuracites and errors, such as from design limitations in the instruments and from misreadings by the operators.
Laser beam systems have also been employed in elevation leveling and grade measurements. One such system provides, in place of the level, a laser beam which rotates in a level or graded plane. The elevation of a point remote from the laser device is measured by use of a rod on which a laser beam detector, including a readout meter, is mounted for manual sliding movement along the rod. The operator moves the detector along the rod to a position at which it is intercepted by the laser beam, as indicated by the meter which is visually read. Such systems are available from Spectra-Physics, Inc. of Mountain View, Cal. under the designation Laser Eye (TM) Grade Tool and Detector. While such systems provide many improvements over the conventional level and rod system, particularly in certain construction projects involving repetitive checking of grade for accuracy, it also presents certain disadvantages and limitations. For example, measurement accuracy is compromised because of the reliance on the operator's skill and judgment in properly positioning and reading the meter. Where used in more accurate and difficult measurement operations, as in elevation surveying, considerable time is required for the surveyor to set up the device and take each measurement. Thus, there is a requirement for a surveying system which will overcome the problems and limitations of existing systems.